Choked shotgun with rifled barrel



Feb; 24, 1970 E. u. LOWRY 3,496567( CHOKED SHOTGUN WITH RIFLED BARRELFiled Jan. 4, 1968 2 Sheets-Sheet E DWARD D. LOWRY INVENTORI ATTORNEYFeb.

Filed Jan. 4, 1968 2 Sheets-Sheet 2 STANDARD SKEET BARREL 1.2

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RAO/AL DSTANCE FROM CENTER OF PATTERN- (IN) i INVENTORZ EDWARD &Low/?y7% exw/7%@ ATTORNEY 3,496,667 CHOKED SHOTGUN WITH RIFLED BARREL EdwardD. Lowry, New Haven, Conn., assignor to Ohn Matheson ChemicalCorporation, a Corporation of Virginia Filed Jan. 4, 1968, Ser. No.695,696 Int. Cl. F41c 21/00 U.S. Cl. 42-78 Claims ABSTRACT OF THEDISCLOSURE An improved barrel for a shotgun having a full choke at itsmuzzle end and rifiing having a rate of twist deter mined by the formulaT=1rBR/P wherein T is equal to the rate of twist in inches perrevolution, B is equal to the bore diameter of the barrel in inches, Ris equal to the desired range in inches, and P is equal to the radius ofthe desired pattern in inches.

This invention relates generally to firearms. More par ticularly, itrelates to a `barrel for a shotgun intended for firing shot or pellets.

A barrel constructed in accordance with this invention is particularlyadapted for a shotgun for use in skeet Shooting. A typical skeet fieldhas two houses which contain traps for throwing the clay pigeons ortargets. One house is called the high house and the other the low house,since one starts its targets high and the other low. The targets fromeach house always follow the same path. The angle of fiight from eachhouse is not directly opposed, but is pointed slightly away from theShooting posts. The two flight lanes tend to cross in the center of thefield some ten feet beyond the line drawn between the houses. There areeight Shooting positions, seven of them being spaced about a semicirclewith the first position at the high house and the Seventh position atthe low house and Stations two through six evenly spaced along thesemicircle between them. The eighth station is positioned at the centerof a line running between the high and the low house. It will thus beseen that all the Shooting positions, except number eight, are equdstantbetween a point where the two target flight lanes cross. Most skeetShooters try to break the target Somewhere near this crossing point. Inview of this fact, and in View of the fact that the shots at the numbereight station are very close, it has been determined that a range of 20yards is the best figure for use in determining the particular patternof the shot. The ideal shotshell attern for use with skeet has beenfound to be that wherein all the pellets in the load would fall withinand be evenly dis tributed across a 30 inch circle at 20 yards.

With conventional ammunition and a typical skeet gun it has 'been foundthat although 75 to 80 percent of the shot will fall within the 30 inchcircle at 20 yards, the distribution of the pattern is such that thedensity of the pellets is very high near the center of the circle andrelatively low at the outer portions of the circle.

Although the degree of choke of a shotgun can influence the dispersionof the shot, it does not appear able to overcome the problem of unevendistribution. For eX- ample, the barrel of a typical skeet gun isusually provided with a cylnder bore or modified choke. A trap gun isusually provided with a full choke. In the case of the skeet gun, 75 to80 percent of the pellets can be placed in a 30 inch circle at 20 yards.The dispersion of the pellets to provide this pattern is causedprincipally by deflections to the pellets which occur'in the muzzle. Asthe column of shot emerges from the muzzle, it is caught between twoforces. Once force is the acceleratng force of the wad acting in thedirection away from the muzzle 3,496,667 Patented Feb. 24, 1970 of thegun and the other force is the decelerating force due to air resistanceactng on the shot in the direction toward the muzzle of the gun. Thesetwo forces acts to compress the shot column and result in lateralmovement of the pellets as they emerge from the muzzle. In the case ofthe full choke barrel, the wad is decelerated due -to the constructionin the barrel and the pellets are in a sense squirted out of the muzzle.Accordingly, the shot col umn is not subjected to the "anvil elfectprevalent in a cylinder bored shotgun with the result that the pelletsstart their journey with all of them traveling toward the center of theeventual pattern. They will, however, be individually deflected due tothe fact that their surfaces are slightly uneven and thus theaerodynamic pressure on each pellet will be unbalanced enough to cause amildly erratic flight. Accordingly, in the case of a full choked firearmthe pellets will not have strayed very far by the time the load reaches20 yards and to percent of the pellets Will pass through a 10 inchcircle at this range. Accordingly, to obtain a attern that is wideenough at 20 yards, a bore is required that will permit the pellets tohave a relatively large degree of lateral movement as they emerge fromthe muzzle.

Accordingly, in view of the discussion above on the causes ofdispersion, most skeet guns have little, if any, choke. However, as hasbeen stated before, even though the dispersion is deemed satisfactory,the density obtaned with the typical skeet gun is not satisfactory sincea high proportion of the pellets are concentrated near the center of thepattern and relatively few near the edges of the pattern.

Accordingly, it is an object of this invention to provide a barrel for ashotgun which will provide the proper dispersion with even distributionacross a given pattern.

More particularly, it is an object of the present invention to provide abarrel for a shotgun which is capable of placing over percent of thepellets from a gven load in a 30 inch circle at 20 yards with relativelyeven distribution across the circle if desired.

Still another object of the present invention is to provide a barrel fora shotgun to be used in connection with the game of skeet which willenhance the chances of breaking a target in the event of an error inain.

These and other objects of the invention may be accomplished through theprovision of a shotgun barrel having a full choke and being rifled fromits muzzle to the shell receiving cham'ber with a twist deemed by theformula T=7rBR/P wherein T is equal to the rate of twist in inches perrevolution, B is equal to the bore diameter of the barrel in inches, Ris equal to the desired range in inches, and P is equal to the radius ofthe desired pattern in inches.

The advantages of the present invention will become more apparent uponthe reading of the following description and by reference to theaccompanying drawings in which:

FIGURE 1 s a transverse cross sectional View of a portion of a gunbarrel embodying the invention;

FIGURE 2 s a transverse cross sectional view taken on the lines 2-2 ofFIGURE 1;

FIGURE 3 is a diagrammatic View showing the relationship of the rangeand desired pattern used in ascertaining the rate of twist of therifling of the barrel; and

FIGURE 4 is a graph comparing the pellet density obtainable with astandard skeet barrel with that of a barrel constructed in accordancewith the present invention.

Referring to the drawings and particularly to FIG- URE 1, the forwardportion of a shotgun barrel 2 is shown. The muzzle end of the bore ofthe barrel 2 is constricted to form what is known in the art `as a fullchoke as indicated at 4. Although the amount of constriction will varyin accordance with the particular gauge of shotgun Table I provides anindication of the internal diameter A of the internal bore through thechoke port on 4 and the internal diameter B of the bore of the barrelfor the various common gauge shotgun barrels.

The entire effective length of the barrel 2 is rifled including thechoke portion 4 thereof. By effective length is meant the length fromthe muzzle end to the forward end of the tapered shotshell receivingchamber. If desired, the chamber could also be rifled, but obviously, itwould not have any effect on the shot charge because of the shell. Thetwist rate of the rifiing is constant throughout its length. In thepreferred embodiment of the invention as shown in FIGURE 2, there areeight rifiing grooves 6 evenly spaced about the internal surface of thebore of the barrel 2. The depth of the grooves 6 may vary somewhatkeeping in mind the fact that if the grooves are too deep, the barrelmay be weakened because of its relatively thin wall thickness. It hasbeen found that a depth of .05 inch is satisfactory.

The rate of twist is determined by taking into consideration the bore Bof the barrel, the desired range, and the desired width of pattern. Asshown in FIGURE 3, points X and Y indicate diametrically opposed pointson the circumference of the pattern. The radius of the pattern isindicated by P. Theoretically, it is desired that .the outermost pelletswould take the path indicated by lines 8 and 10 and hit the pattern atpoints X and Y. However, the theoretical is not attainable due toaerodynamic pressure so that between 80 and 90 percent of the pelletsare within the pattern area. R indicates the range which is the distancefrom the end of the bore of the barrel to the center of the pattern.

In accordance with this invention it has been determined that the rateof twist for a full choked shotgun barrel can be determined by theformula T=7rBR/P, where T is equal to the twist rate in inches perrevolution, B is equal to the bore diameter in inches, R is equal to therange in inches, and P is equal to the radius of the desired patterncircle in inches, and 'r is equal to the standard dimension ofapproximately 3.1416.

As has been discussed above, for skeet Shooting, it is desired that ahigh proportion of the pellets should be contained within a patternhaving a 30 inch diameter at a range of 20 yards. Accordingly, whenrifiing a barrel in accordance with the preferred embodiment of thisinvention the twist rate will be determined by the above formula with Bbeing the bore diameter of the particular gauge gun, the range being 20yards or 720 inches, and P, the radius of the pattern circle, beingbetween 12 and 15 inches. In the case of the exceptional shooter it maybe desirable to reduce P to a value below 12 inches down to about 10inches.

Table II, set forth below, gives the range of desirable twist rates forvarious gauges as calculated by using the above formula with the borediameter as set forth in Table I, a range of 720 inches, and a patternradius of from 12 to 15 inches TABLE II Twist Rate Gauge: (inches/re 12110 to 138 28 83 to 104 .410 61.8 to 77.2

It is to be understood that in the case of the exceptional shooter, thevalue of P can be as low as 10 inches. In this case, the upper value ofthe Twist Rate shown in Table II would be increased.

As shown by Table III, it will be seen that the twist rate of the rifiinof the present invention is substantially higher than that used inrifies of the type firing a bullet.

TABLE III Twist Rate Caliber: (inches/rey.) .22 short 24 .22 long rifle16 .220 swift 14 .30/30 12 .30/06 10 .32 special 16 .375 magnum 12Accordingly, it must be appreciated that the rifiing used in the presentinvention is not of the same twist rate as normally used, and thuscannot be considered the normal degree of rifiing as commonlycontemplated in the art.

FIGURE 4 graphically depicts the pattern results of a standard sheetbarrel and the improved rifled full choked shotgun constructed inaccordance with the present invention. For the purpose of comparison theshotgun constructed in accordance with this invention had a 12 gaugefull choked barrel and a twist rate of 129 inches per revolution.

As can be seen from FIGURE 4, with the standard skeet barrel the pelletdensity is highest in a range from about 0 to 2 inches from the centerof the pattern and steadily decreases as you move farther away from thecenter. The improved shotgun having a barrel constructed in accordance*with the present invention has a lower pellet density in the range from0` to 2 inches, but the density remains fairly even as you move awayfrom the center of the pattern up to about 10 inches where it beginstapering off. However, in the range of from 8 to 14 inches from thecenter of the pattern, the pellet density is greater than that of thestandard skeet barrel. The standard skeet barrel will place about 75percent of the total shot in a 30` inch circle at 20 yards. With thefull choked barrel of 129 in./rev., about 86.4 percent of the pelletsare placed in a 30 inch circle at the same range. Accordingly, with thepresent invention not only is the distribution of the pattern betterthan that of a standard skeet barrel with a higher proportion of thepellets landing in the desired pattern radius, but also, thedistribution of the pellets within the pattern is better due to the factthat the density throughout the entire pattern is more constant and morepellets are positioned near the periphery of the pattern.

As a further example of the eectiveness of this invention, a pluralityof 12 gauge full choked shotguns were fired with their barrels rifled ata twist rate of 143 inches per revolution. With these firearms, about89.5 percent of the total shot was placed in a 30` inch pattern at 20yards. As shown in FIGURE 4, the distribution of the pellets is similarto that of the barrel having a twist rate of 129 inches per revolution,except that the density was higher. Thus rifiing in a 12 gauge shotgunof about 145 inches per revolution would be advantageous under certaincircumstances.

The combination of the rifiing and the full choke results in theimproved pattern characteristics. Due to the rifiing, the shot charge isrotated about its axis giving each pellet a peripheral velocity. Thisvelocity is directly proportional to the distance of the pellet to theaxis of the bore of the barrel. Thus, the outstide pellet will betraveling twice as fast as the pellets intermediate the outside layerand the center. As the column of shot leaves the muzzle, each pelletwill keep its peripheral velosity which is now a velocity directed in astraight line going away from the pattern center. '1'hus, by giving thebarrel the proper riing, so that the outside pellet travels inchesoutwardly by the time the whole load has traveled yards, the pelletsshould all be evenly distributed across a inch circle. However, in orderto make this work it is necessary to eliminate all sources of dispersionof the pellets. Accordingly, the barrels must be full choked so as toelminate the anvil efiect described above. However, due to the unevenessof the pellet surfaces, the aerodynamic pressure on each pellet will beunbalanced causing a slightly erratic fiight with the result that thetheoretically possible perfect pattern of percent and even distributioncannot be obtained. However, as indicated above, it is possible toobtain 89.5 percent of the pellets in a 30 inch circle at 20 yards witha distribution that is more even than that obtainable with the standardskeet barrel.

What is claimed is:

1. In a shotgun, a barrel having a shotshell receiving chamber adjacentone end and a full choke at its muzzle end, the bore diameter of saidbarrel being about .730 inch, said choke having an internal diameter ofbetween about .694 to .699 inch, said barrel being rified at least fromthe muzzle end of the choke to the forward end of the shotshellreceiving chamber, said rifiing having a rate of twist of from to inchesper revolution.

2. In a 16 gauge shotgun, a barrel having a shotshell receiving chamberat one end and a full choke at its other end, said choke having aninternal diameter of between about .640 to .645 inch, said barrel beingrified at least from the muzzle end of said choke to the forward end ofsaid shotshell receivng chamber, said rifling having a rate of twist offrom about 101 to about 121 inches per revolution,

3. In a 20 gauge shotgun, a barrel having a shotshell receiving chamberat one end and a full choke at its other end, said choke having andinternal diameter of between about .590 to .595 nch, said barrel beingrified at least from the muzzle end of said choke to the forward end ofsaid shotshell receiving chamber, said rifling having a rate of twist offrom about 92.7 to about 116 inches per revolution.

4. In a 28 gauge shotgun, a barrel having a shotshell receiving chamberat one end and a full choke at its other end, said choke having aninternal diameter of between about .528 to .532 inch, said barrel beingrifled at least from the muzzle end of said choke to the forward end ofsaid shot shell receiving chamber, said rifiing having a rate of twistof from about 83 to about 104 inches per revolution.

5. In a .410 gauge shotgun, a barrel having a shotshell receivingchamber at one end and a full choke at its other end, said choke havingan internal diameter of between about .390 to .393 inch, said barrelbeing rified at least from the muzzle end of said choke to the forwardend of said shotshell receiving chamber, said rifiing having a rate oftwist of from about 61.8 to about 77.2 inches per revolution.

References Cited UNITED STATES PATENTS 592,437 10/ 1897 Oberhammer 42-78BENJAMIN A. BORCHELT, Primary Examiner CHARLES T. JORDAN, AssistantExaminer U.S. Cl. X.R. 42-79

